Methenamine Hippurate (Hiprex) Side Effects

Possible adverse effects of methenamine are listed below. Call your doctor for medical advice if they are severe or persistent.

• Upset stomach
• Stomach cramps
• Vomiting
• Diarrhea
• Loss of appetite  

Methenamine can also cause more serious side effects. Call your doctor immediately or seek emergency medical attention if you develop:

Signs of an allergic reaction (skin rash, hives, itching)

The above list may not include all the potential side effects of methenamine. Contact your healthcare provider if your side effects are unusual or severe or they do not get better over time. You can also report unusual side effects to the Food and Drug Administration at 1-800-FDA-1088.

Methenamine (Hiprex) Overdose: In case of an overdose, call your doctor immediately. You can also call your local poison control center, provincial poison control center, or the national poison control center at 1-800-222-1222. Call 911 if someone has lost consciousness, collapsed, is not breathing, or has had a seizure.

Source: FDA